Epson Y16499100301 - Manual (Page 31)

The power indicator above the keyboard lights up, and
after a few seconds, the computer begins to perform an internal
self test. This is a diagnostics program the computer runs
whenever you turn it on. The power-on diagnostics self test
checks the RAM (random access memory), keyboard, system
board, and peripherals before the computer begins normal
operation.
For a complete description of the power-on diagnostics, see
Appendix C.
Adjusting screen contrast and brightness
If you cannot see text on the screen clearly, use the switch
or switches on the right side of the screen to adjust the screen’s
contrast (and brightness). The standard model has only the
contrast switch. The backlit model has a contrast switch and a
brightness switch, as shown below.
The contrast switch determines how brightly the characters
display against the background. To increase the contrast, move
the switch up. To decrease it, move the switch down.
1-16 Setting Up Your System